It is known that many materials, such as carbon/carbon composites, carbon fibers, graphite, and certain metals, have properties which make them attractive for use in aerospace and other applications in which their susceptibility to oxidative deterioration at elevated temperatures is a serious disadvantage. It would be desirable to find a means of protecting those materials from oxidation at high temperatures, and it has been proposed to provide such protection with ceramic coatings. However, known ceramic coatings have proved to be inadequate.
Copending applications Ser. No. 242,493 (Niebylski-I), filed Sept. 9, 1988, and Ser. No. 272,481 (Niebylski-II), filed Nov. 17, 1988, and now U.S. Pat. No. 4,921,925 teach organoborosilazane polymers which can be coated onto substrates and pyrolyzed to ceramics to provide improved protection from oxidative deterioration at elevated temperatures; and copending application Ser. No. 261,104 (Niebylski-III), filed Oct. 24, 1988, teaches that coating compositions comprising the organoborosilazane polymers can be improved by the incorporation therein of a mixture of aluminum-silicon eutectic, silicon carbide, silicon boride, and silicon metal. However, the utility of these compositions is limited by the moisture sensitivity of the ceramics obtained from them.